Bearers for solid of revolution tanks on board ships

ABSTRACT

Load bearers for bearing solid of revolution tanks having vertical axes of revolution on board ships, comprising continuous peripheral structure arranged around the tank and positioned in the equatorial area thereof, two bearer and coupling members surrounding the tank and each being coupled by one of their edges to the peripheral structure and by the other to a bearer member of the ship so that the forces perpendicular to the axis of revolution of the tank are absorbed by at least one of the bearer and coupling members and the forces parallel to the axis of revolution of the tank are absorbed by both the bearer and coupling members, one of which works under traction and the other under compression so that whatever the interspacing between the bearer and coupling members and the tank may be, bending moments will not be induced in the tank, said peripheral structure being coupled to the tank so that at least the inner peripheral part of the structure forms part of the tank.

Unite States Urruela atet 1 1 1 Oct. 15,1974

[ BEARERS FOR SOLID OF REVOLUTION TANKS ON BOARD SHIPS Assignee: Tecnica Sener Industrialy Y Naval,

S.A., Las Arenas, Spain [22] Filed: Apr. 10, 1973 21 Appl. No.: 349,723

[30] Foreign Application Priority Data Apr. 13. 1972 Spain 401734 [52] US. Cl. 114/74 R, 220/9 LG, 248/D1G. 1, 248/146, 62/55 Primary EXaminer-Trygve M. Blix Assistant Examiner-Sherman D. Basinger Attorney, Agent, or Firm-Fleit, Gipple & Jacobson 57 ABSTRACT Load bearers for bearing solid of revolution tanks having vertical axes of revolution on board ships, comprising continuous peripheral structure arranged around the tank and positioned in the equatorial area thereof, two bearer and coupling members surrounding the tank and each being coupled by one of their edges to the peripheral structure and by the other to a bearer member of the ship so that the forces perpendicular to the axis of revolution of the tank are absorbed by at least one of the bearer and coupling members and the forces parallel to the axis of revolution of the tank are absorbed by both the bearer and coupling members, one of which works under traction and the other under compression so that whatever the interspacing between the bearer and coupling members and the tank may be, bending moments will not be induced in the tank, said peripheral structure being coupled to the tank so that at least the inner peripheral part of the structure forms part of the tank.

15 Claims, 12 Drawing Figures PATENTED [IN 1 51974 SHEET 1 0f 8 I smears PATENIEnnm 1 51914 PATENTEU l 5974 3.841 .269

SHEEI EMF 8 fl .2 8 l j /W M PATENTEDUET 1 51974 SIIEH 80F 8 FIG. 11

BEARERS FOR SOLID OF REVOLUTION TANKS ON BOARD SHIPS BACKGROUND OF THE INVENTION This invention relates to improvements in bearers for self-strengthened tanks in the shape of solids of revolution having vertical axes of revolution on board ships and buoyant bodies which are designed to transmit to the resistant member or structure of the ship or buoyant body concerned the weight of the tank without producing in practice bending moments in the shell or wall of the aforesaid tank.

These tanks can take any solid of revolution shape, having a vertical axis of revolution and they may be spherical, cylindrical with spherical or ellipsoidal tops, or else formed by a combination of the aforementioned geometrical shapes.

In accordance with any of the shapes indicated, these solid of revolution shaped tanks are. particularly suitable for storage and/or carriage of pressurized liquid gas due to their low ratio of surface area to volume and to the fact that their walls are predominantly working under membrane stressing without major bending moments or shear stresses being introduced. All this contributes to the tank weights being relatively low according to the shapes described, this having considerable bearing on their cost. a

In the case of liquids or liquefied gas stored and/or carried at pressure close to atmospheric, the solid of revolution tanks of the abovementioned shapes offer the advantage of their low surface-to-volume ratio and also to a lesser degree the advantage that they are fundamentally working as membranes. The fact that the bending moments and shear stresses may be relatively more important when the pressure is of atmospheric order does not cause major difficulties inasmuch as, due precisely to the relatively simple geometric shape and the absence of stiffeners interrupting homogeneity of the tank shell, it is possible to calculate very accurately the status of stresses on each point of the tank for any cargo load situation.

All this gives greater reliability in the design of tanks, to a point where for solid of revolution tanks designed on the basis of a very accurate analysis of the stress condition at each point, the Classifying Societies and other governing bodies permit their installation on board ships or in buoyant bodies without requiring the installation of a full secondary barrier to contain contingent leaks from the main tank, which arebecoming obligatory in other tank types.

The possibility of wholly or partially eliminating the secondary barrier aforementioned and the economy in material that can be achieved, makes the adoption of tanks in the form of a body of revolution particularly attractive in harmony with the shapes abovementioned, for the ocean transport of natural liquid gas, ethylene, propane, propylene, butane, butadiene, isobutane, ammonia, chlorine and other liquid products carried under pressure not very much above atmospheric, particularly in those cases where the boiling point at atmospheric pressure is very low. Such is the case of liquid natural gas carried at less than 162 C., of ethylene at less than 105 C., and other liquid petroleum gases carried between 45 C. and 50 C. In all these cases of low-temperature carriage the tanks are insulated to prevent excessive evaporation of the product.

The geometrical configuration and the materials: to be used in the cargo tanks, their bearer systems and the ships supporting structure must be such that at no point are temperatures reached below those at which brittleness fracture may occur, at the same time allowing thermal contraction of the tanks, which occurs when the temperature drops below ambient to that of the individual product carried.

One of the most important problems that the use of the vertical axis, body of revolution type tank brings up on board is that of the footing, due to the ship's movement at sea, this setting up inertial pressure not only in the direction parallel to the axis of revolution of each tank but also in directions parallel to the longitudinal and transverse axes of the ship or buoyant body. The problems becomes particularly acute in the case of large ships designed for the carriage of liquid natural gases because of the large dimensions of the tanks, which are saddled with large inertia pressures.

Several arrangements for tank footings on board ships are already known. As examples, the Norwegian Pat. Nos. 4145/69 and 4146/69 can respectively be quoted, also Spanish Pat. No. 368,210 which claims priority in French application Pat. Nos. 157,299 of 28 June 1968 and Pat. No. 180,260 of 24 Dec. 1968.

The first of these patents describes a device for carrying tanks on board ships, consisting of cylindrical plates welded direct to the foundation and to the tank shell, where these plates can be continuous between tank and foundation or else non-continuous with an intermediate supporting wing fitted with coupling devices preventing the relative movement between upper and lower parts of the support or bearer. In such patents there is also the provision of an equatorial or middle ring or collar forming an integral part of the tank, this having an outer foot attached to the skirt or flange to form part of the bearer. The tank is thus held non-concentrically on the line of the circumference, causing major bending moments to be induced on the tank shell by the action of stresses parallel to the axis of revolution.

The bending moments induced and the dimensions of the middle or equatorial part, according to the preferable working method of the aforesaid patents, result in the system being impracticable for large-dimension tanks.

In Spanish Pat. No. 368,210, the tanks are held by means of a relatively large number of discrete members preferably arranged along the middle-line or equator and perpendicular meridians.

Although no bending moments of importance are induced in the shell with this method, strong concentrations of stresses are in fact originated in the link areas between shell and the aforementioned discrete members, which also makes this methodimpracticable for large-dimensioned tanks.

SUMMARY OF THE INVENTION The purpose of the present invention is to achieve a bearer allowing the installation of body of revolution type tanks on board ships without the danger of bending moments or major stress concentrations being induced'in the shell, this type of bearer thus permitting erection of the tank without practical restriction on dimensions, and with greater safety.

According to the present invention, the support consists of a continuous peripheral structure arranged around the tank, located in its equatorial or middle area, from which two bearing and coupling members root out to the bearer structure. These bearing and coupling members surround the tank and are separated one from the other in the direction perpendicular to the axis of revolution of the tank. The two members aforementioned are connected by one of their edges to the peripheral structure mentioned and by the other to the ships structure or bearer structure.

Coupling of the bearer means and coupling to the ships structure or bearer detail can be positioned below the equatorial or middle area of the tank, close to the double bottom of the ship, or above the middle area close to the upper deck. In the first case the tank will be supported on the bearer detail and in the second suspended from it.

The aforementioned peripheral structure is coupled to the tank so that the inner peripheral part of the aforesaid structure forms part of the tank.

Using this method, the stresses perpendicular to the axis of revolution of the tank, i.e., those directed on planes parallel to the base plane of the ship, are transmitted in the form of shear stresses through the peripheral structure, passing from it to one or both supporting members and coupling, also in the form of shear stresses. Thus, correlative action between the peripheral structure and the tank shell, derived from the action of forces perpendicular to the axis of revolution does not in practice induce bending moments in the tank shell. Transmission of shear stresses from the peripheral structure to the bearer structure is made through the supporting member(s) which has (have) circumferential continuity throughout the whole of the web.

Insofar as forces parallel to the tanks axis of revolution are concerned, also transmitted through the peripheral structure, these forces are absorbed and transmitted to the bearer structure of the ship by the assembly comprising the two bearing and coupling members, one of which will work under compression, while the other will work under traction. Due to this joint form of working of the two bearing and coupling members, the mutual action between peripheral structure and tank shell as derived from the action of forces parallel to the axis of revolution does not in practice induce bending moments in the tank shell, distinct from what would occur if only a single bearer and coupling member were employed, in which event major bending moments would appear due to non-concentricity of the line of reaction application in respect of the shell half surface.

Thermal contraction of the tank, appreciably similar to that in the peripheral structure which is at the same temperature as the tank shell, is possible thanks to the existence of a temperature gradient in the two bearer and coupling members, the temperature of which rises from the edge coupled to the peripheral structure to that joined to the ships bearing structure. However, the bearer and coupling details lack stiffeners in the area closest to the tank peripheral structure, resulting in low rigidity in comparison with the peripheral structure, the whole of the bearer system becoming thermally deformed so that the peripheral structure can follow the tank shell, keeping it appreciably parallel to itself. This results in both the normal forces on the tank and the bending moments induced by thermal contraction being of low magnitude, hence the oversize or allowance of the tank shell in the vicinity of the middle or equatorial line are of moderate magnitude.

The two bearing and coupling members will be continuous in the coupling area with the peripheral structure, one of the members furthermore being continuous throughout its length, preferably the one working in compression.

Between the two bearing and coupling members are stiffeners contained on meridian planes of the tank, these being defined between the carrier structure and a diaphragm or ring located close to the peripheral structure, in an area where both bearing and coupling members are continuous. Between this bearer structure and the ring or diaphragm aforementioned one or more rings can be fitted, these running between the bearer and coupling members, which together with the aforementioned stiffener give stability to these bearer and coupling members.

The peripheral structure may consist of at least one open section-shape whose general configuration offers a continuous web, preferably horizontal, from which four also continuous shoulders or projections project out, three of them towards one side of the web and the fourth to the other, at least the two end shoulders located on the same side projecting out from the free edges of the web, the whole of these projections or shoulders serving as coupling for the peripheral structure to the tank shell and to the bearing and coupling members.

The section stubs to which the tank shell is attached become a part of it, the other stubs located around the tank being for coupling to the bearer and coupling members. The section web comprising the peripheral structure lies preferably in the radial direction, perpendicular to the tank axis of revolution.

The stubs or projections attached to the tank shell to form part of it are the inner projections or stubs of the three located to one side, and the stub emerging from the other side of the web.

The projection or wing emerging alone from one of the web sides can occupy different positions in relation to it, so that only the stubs attached to the tank shell become part of it, or rather these stubs together with part or whole of the web section or shoulder.

Thus, for example, the stub turned in the direction opposite to the other three can project'out from the inner edge of the web, becoming an extension of the opposite stub projecting out from that edge, both stubs becoming part of the tank shell, while the other two outer studs serve as coupling to the bearer and coupling members.

On the other hand, the stub turned in the direction opposite to the other three can project out from the outer edge of the web to come together with the opposite stub projecting out from the inner web edge and, with this web, forming part of the tank shell, the other two stubs as in the previous case remaining for fixing to hearing and coupling members.

Between these two positions, the aforementioned stub turned in the direction opposite to the other three can project out from an intermediate point of the web to form part of the tank together with the opposite stub projecting out from the inner web edge, and with the part of the web running between these two inner and intermediate opposite stubs, serving as bearing and coupling members as in the previous cases. In this event, the stub turned in the direction opposite to the other three will preferably project out from a point opposite to the center opposite stub to become and extension of it.

When the peripheral structure is made up of two or more open section-shapes, the end of the section farthest away from the bearer structure has a continuous web from which four continuous stubs project out, while the remaining sections consist of a continuous web from which six also continuous stubs or wings project out.

Of the end-section stubs farthest away from the bearer detail, three of these are turned towards the adjacent section and the fourth in the opposite direction, to become part of the tank shell together with the inner stub of the other three opposite.

Of the six stubs on the remaining sections, three are located on each side, preferably as extensions, the inner stubs (one on each side) being used to form part of the tank shell.

The other four stubs of the intermediate sections, two on each side, face the intermediate or end section stubs, these not forming part of the tank shell, for coupling to them by means of intermediate revolution members.

Lastly, the end section stubs closest to the bearer structure, turned towards that structure, face the bearing and coupling members for coupling to them.

Here, as in the case of the peripheral structure formed by a single open section, the stub turned in the direction opposite to the other three, on the section farthest away from the bearer structure, can be positioned at the inner end of the web, on the outer end or at an intermediate point, only the two opposite intermediate stubs or also the whole or part of the web then becoming part of the tank in this section.

The peripheral structure can also consist of a series of at least three independent continuous sections or shoulders, horizontal and parallel and of different diameter, forming vertices of a triangular section, these sections being interconnected by means of intermediate revolution members defined in section by the sides of the triangle aforesaid, providing the sections with continuous stubs for their coupling to the intermediate members aforementioned, to bearer structure and coupling to the tank shell.

Within this makeup, the circumferences associated with the inner and outer sections will preferably be coplanar, the intermediate coupling detail between these sections consisting of a circular ring.

Of the three sections forming part of the peripheral structure, the intermediate takes a general Y-shape, each of its two wings or shoulders being turned towards one of the two end sections for their coupling to the matching flanges or edges of the intermediate revolution members of the peripheral structure, while the web is turned towards the bearer and coupling member closest to the tank, for coupling to the flange or edge of that member.

Of the other two sections, one of these has three continuous stubs or projections and the other four of these stubs, while the outer section can be the one fitted with four stubs and the inner with three, or vice versa.

In this case, when it is the outer section which is fitted with four continuous projections or stubs, two of these stubs are turned towards the other two peripheral structure sections for their coupling to its intermediate member, while of the other two stubs one is turned towards the outer bearer and coupling member for coupling to it, and the other towards the free flange or edge of the matching tank shell, also for coupling to it. In this case, the two stubs mentioned in last place are found turned in the opposite direction as extension between themselves. The inner section, which in this case has three stubs, has two of these stubs turned towards the other two peripheral structure sections while the third stub is turned towards the free edge or flange of the other part of the tank shell for coupling to it.

In the second case, when it is the inner section that has four continuous stubs, two of these stubs are turned towards the other two peripheral structure sections for coupling to the intermediate members thereof, while the other two stubs are turned towards the free edges of the shell halves or upper and lower parts of the tank for their coupling to them, also in this case these two stubs extended.

The outer section, while will now have three continuous stubs, has two of these turned towards the other two peripheral structure sections, while the third stub is turned towards the outer bearer and coupling member for linkage with it.

In the first case, the aforementioned end section stubs and the matching intermediate coupling member between these sections become part of the tank shell, while in the second case only the inner section stubs turned for coupling to the tank shell form part of the tank shell.

The peripheral structure can also be made up of four continuous sections running according to horizontal and parallel circumferences defining the vertices of a quadrilateral section, the sections running as two of the opposed vertices (the upper and lower), assuming a general Y-shape, the wings or shoulders of which are turned towards the adjacent intermediate sections, while the web of both is turned outwards for coupling to the free edge or flange of the adjacent tank half, the one to the flange or edge of the bearer and inner coupling member, the other. The sections running as the other two vertices each have three continuous stubs, two of which are turned towards the adjacent sections of the two aforementioned vertices, and the third towards the tank flange or edge for coupling to the shell in the section that is positioned on the inner side, while in the section located on the outer side this third stub is turned towards the bearer and coupling outer member for linkage with the free edge or flange adjacent it.

' turned towards the opposite section for its coupling by means of an intermediate coupling member taking care of stiffening the whole. As in the other cases, the distinct sections are interconnected by intermediate revolution members joined by the edges or flanges to the matching continuous stubs or projections.

In this case, the outer stub of one of the Y-sections and one of the inner section stubs become part of the tank shell, apart from the intermediate revolution member coupling the two aforementioned sections.

The diaphragm or ring aforementioned, next to the peripheral structure, together with this peripheral structure and with the continuous part of the bearer and coupling details running between the aforementioned diaphragm and peripheral structure define a conduit in which a coolant can be introduced at an intermediate temperature between ambient and that of the cargo to be carried, for the purpose of pre-cooling the peripheral structure and the middle or equitorial area of the tank before loading, allowing carrying out the loading operation with greater speed without the danger of thereby inducing excessive heat stresses in the tank and bearer.

This pre-cooling ability is particularly attractive in the case of carrying liquid natural gas at l62 C., a coolant consisting of nitrogen-gas being possible at a temperature in the order of 80 C. inasmuch as its availability in liquid form at l96 C. is normal in this type of vessel.

If the peripheral structure consists of two or more sections, one or more conduits can be formed between these and the intermediate coupling members to be similarly used for the introduction of coolant.

The coolant fluid can be introduced at one or more points, also providing an outlet for it at one or more points, so that a uniform flow is in any event obtained, where a palpably uniform circumferential distribution is achieved.

All the characteristics and structure described above will become manifestly clear with the following description given with reference to the enclosed drawings, on which are shown several embodiments given by way of non-restrictive example.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic vertical sectional view taken through the center of a spherical tank mounted on a bearer built pursuant to the prevent invention for installation on board ship.

FIG. 2 is an enlarged view showing the peripheral structure of FIG. 1 coupled to the tank and to the bearer/coupling members.

FIG. 3 is a schematic vertical sectional view similar to FIG. 1 but showing a variation of the spherical tank and bearer structure.

FIG. 4 is an enlarged view similar to FIG. 2 but showing the peripheral structure of FIG. 3.

FIG. 5 is a schematic vertical sectional view similar to FIGS. 1 and 3 but showing yet another variation of the spherical tank and bearer structure.

FIG. 6 is an enlarged view similar to FIGS. 2 and 4 but showing the peripheral structure of FIG. 5.

FIG. 7 is an enlarged vertical sectional view similar to FIGS. 2, 4 and 6 but showing yet another variation in the peripheral structure coupled to a spherical tank and bearer/coupling members.

FIG. 8 is a schematic vertical sectional view taken through the center of a spherical tank mounted on another bearer built in accordance with the present invention.

FIG. 9 is an enlarged view showing the peripheral structure of FIG. 8.

FIGS. 10 and 11 are similar to FIG. 8 but show a variation of the spherical tank and bearer structure.

FIG. 12 is a schematic vertical sectional view similar to FIGS. 8, 10 and 11, but showing another variation in the spherical tank and bearer structure.

DETAILED DESCRIPTION OF THE DRAWINGS As can be seen in the drawings, the spherical tank 1 is set on a bearer consisting of a peripheral structure 2 and two bearer and coupling members 3 and 4.

The peripheral structure 2 is continuous and extends around the tank 1, positioned on its middle or equitorial area.

The bearer and coupling members 3 and 4 encircle the tank, and are separated in a radial direction. These members are coupled by one of their edges or flanges to the peripheral structure 2 and by their opposite edges or flanges to the bearer structure 5. The peripheral structure 2 is in turn joined to the tank 1 so that at least the inner peripheral part of that structure forms part of the tank shell.

With the arrangement described, the forces perpendicular to the vertical axis of revolution of the tank are absorbed by one of the members 3 or 4, while the forces parallel to the vertical axis of revolution are absorbed by the two members, one of which will be in traction and the other in compression, bending moments not being induced on the tank shell.

The bearer and coupling members 3 and 4 are continuous at least in the peripheral structure 2 coupling area; at least one of these members, preferably the one working under compression, being continuous throughout its length.

Two stiffeners 30 are fitted between the bearer and coupling members 3 and 4 depending upon the meridian or longitudinal planes of the tank 1, restricted by the bearer structure 5 and by a ring or diaphragm 31 between members 3 and 4 and in order, together with the stiffeners 30, to provide stability to these members 3 and 4.

Both the stiffeners and rings aforementioned are shown only in FIG. 1 and partially in 2, their structure having been omitted from the remaining figures for the purpose of convenient illustration.

In the particular case of FIG. 1, the peripheral structure 2 consists of a continuous open section or shape, which, as best seen in FIG. 2, introduces a continuous web 6, preferably in the horizontal position, and a series of continuous stubs or wings 7, 8, 9 and 10. Of these continuous stubs or projections, those marked with reference numerals 7, 8 and 9 are turned in one direction, while stub 10 is turned in the opposite direction. The stubs 9 and 10 project out from the inner edge of wing or shoulder 6, are continuous and face the edges or rims of the two halves 11 and 12 of the tank 1 and are welded to them. The stubs or projections 7 and 8 face the matching edges or flanges of the bearer and coupling members and are welded thereto.

The continuous stub or projection 10 can assume different positions. Thus for example, it can be fitted to the outer end facing stub 7 as shown in FIGS. 3 and 4.

As in the case of FIGS. 1 and 2, stubs 9 and 10 are coupled to the edges or rims of the tank halves 11 and 12, while the continuous projections or shoulders 6 and 8 are coupled to the bearer and coupling members 3 and 4. In this case, not only stubs 9 and 10 become part of the tank shell, but also the web or shoulder 6 of the peripheral structure, the upper part of the tank 12 therefore being of greater radius than the lower part 11, as is clearly seen in the figures.

The continuous shoulder or projections 10 can take an intermediate position between these two end positions, preferably opposite shoulder-stub 8 as shown in FIGS. 5 and 6.

In this case, apart from stubs 9 and 10, the part of the web or shoulder included between these stubs becomes part of the tank shell.

The structure shown in FIGS. 3 and 4 can be utilized for the carriage of fluid at low pressures close to atmospheric. The structure shown in FIGS. 5 and 6 can serve for the carriage of fluids at low or medium pressures, and the structure shown in FIGS. 1 and 2 can serve for low, medium or high pressures.

FIG. 7 shows a peripheral structure consisting of two sections or shapes of configuration similar to those shown in FIGS. 1 to 6.

In this case, two open contour sections are arranged in parallel and comprise continuous webs or shoulders 6 and 6". The first of these has four stubs 7', 8, 9' and 10' and the second has six stubs 7", 8", 9", 10', 13 and 14.

The inner stubs 9' 10' and 9 10" are those joined to the tank shell which includes an intermediate strip 15 between stubs 9 and 10".

Stubs 7 and 8" are linked to the bearer and coupling members 3 and 4. A number of intermediate details l6 and 17 are fitted between stub 7' 14 and 8' 13 ensuring continuity of the bearer and coupling members from shoulder section 6'.

Stub 10' can occupy any one of the positions described in FIGS. 3 and 5. As will be easily understood, the peripheral structure can consist of more than two sections similar to those described.

FIG. 8 shows the same tank 1 equipped with a peripheral structure of different shape resting on the same bearer and coupling details 3 and 4, these being secured at the bottom of the bearer member 5.

The peripheral structure in FIG. 8, as can be seen in FIG. 9, comprises three continuous section members 18, 19 and forming three concentric enclosures, of which those associated with section members 18 and 19 are coplanar, while those associated with section member 20 are positioned on the side of the bearer and coupling members.

Section members l8, l9 and 20 have a number of continuous projections or stubs. Section member 20 has a general Y-shaped configuration, the wings of which are turned towards the other two section members 18 and 19, while the web or shoulder is turned towards the inner bearer and coupling member 4.

Section member 19 has three stubs, one turned towards section member 18, another towards section member 20, and another in the case of FIG. 8 towards the outer bearer and coupling member 3. For its part, section member 18 has four stubs, one of which is turned towards section member 19, another toward the section member 20, while the other two stubs appearing are turned towards the upper part 12 and lower part 11 of the tank, for coupling to the rim or flange of the shell of these halves. The section members are interlinked by intermediate revolution members 21, of which the one that runs between section members 18 and 19 consists of a circular ring when section members l8 and 19 are coplanar, while the others have a truncated conical shape.

In FIG. 10 there is shown a format similar to that of FIG. 8, with the difference that the circumferences are not coplanar and that the support and coupling elements 3 and 4 are constituted by the combination of cylindrical and frustoconical parts.

FIG. 11 shows a tank made up of two different radius halves or parts, the one positioned towards the side of the bearer and coupling members 3 and 4 being of lesser radius. The peripheral structure in this case has the same configuration as the peripheral structure shown in FIG. 8, with the only difference being that section member 18 is the outer section member so that one of its wings is secured to the edge or rim of the upper tank part 12, while the opposite section member is linked to the outer bearer and coupling detail 3, its other two wings being turned towards section members 19 and 20. On the other hand, the inner section will be member 19 fitted with three wings having two towards section members 18 and 20 and the third towards the edge or rim of the tank lower half 11.

In this FIG. 11 arrangement, apart from the sections 18 and 19, the intermediate coupling member 21 between these section members becomes part of the tank shell.

FIG. 12 shows another variation in which the peripheral structure comprises four continuous section members 22, 23, 24 and 25 running as concentric enclosures sectionally defining the vertices of a quadrilateral.

Two of these circumferences will be coplanar, preferably those associated with section members 22 and 24, while the other two circumferences associated with section members 23 and 25 may or may not be in the same vertical plane.

The section members 23 and 25 assume a general Y- shape, with their wings turned towards the adjacent associated section members 22 and 24, while the web remains turned outward for its coupling at section 25 to the inner bearer and coupling member 4 and at section 23 at the edge or rim of the tank part or half 12. Of the three section member 24, wings, two are turned towards the edge or rim of the tank part 11 for coupling to it. The diverse sections are interlinked as in the case of FIGS. 8, 9, 10 and 1 1, by means of intermediate revolution members 21.

Here sections 23 and 24 and the intermediate revolution member linking these sections become part of the tank.

Apart from this, two of the opposed section members, preferably section members 22 and 23, have another inner facing wing 21' designed to strengthen the peripheral structure.

In all cases described, coupling of the bearer and coupling members 3 and 24 with the carrier structure 5 has been shown underneath the middle or equatorial area of the tank, meaning that the tank rests on the bearer member. However, this coupling area could be placed above the equatorial area, the tank then being suspended from the bearer member by means of the same bearer and coupling members and with the same peripheral structures. This arrangement could be shown by nothing more than reversing the figures.

Referring to FIGS. 1 and 2, making the bearer and coupling members 3 and 4 continuous, at least in the area located between the peripheral structure 2 and the ring 31 forms a conduit 26 between these members in which a coolant fluid can be introduced for pre-cooling the tank and peripheral structure.

In the case of FIG. 7, this conduit 26 can be formed between the web 6", the ring 31 (not shown), and the members 3 and 4, or else, preferably, between webs 6' and 6", the ring 31 (not shown), and the intermediate coupling members 16 and 17.

Lastly, in the case of FIGS. 8 through 12, the conduit 26 can be defined by the ring 31 (not shown), the members 3 and 4 and the intermediate members coupling the peripheral structure sections to the aforementioned members 3 and 4; or else preferably by the peripheral structure itself or part of it.

In all cases, the conduit 26 will be fitted with coolant inlet and outlet openings, these openings being cuttable in any one of the members circumscribing the assembly.

The arrangements hereinabove stated are subject to modifications in detail insofar as they do not alter the fundamental principles upon which the present invention is based.

I claim:

1. The combination comprising:

1. A cargo tank having a tank shell and a central vertical axis, said cargo tank adapted to contain liquified gas and including a. continuous peripheral structure means having upper and lower continuous stubs integrally connected with upper and lower portions, respectively, of the cargo tank shell thereby forming an annular portion of the tank shell in the vicinity of the horizontal mid-plane of the cargo tank, said continuous peripheral structure means extending in a lateral sense with respect to the vertical axis of the cargo tank and 1. defining two peripherally continuous protrusions each laterally spaced from one of said portions of the cargo tank shell, said two continuous protrusions being spaced laterally relative to the vertical axis of the cargo tank and with respect to one another,

2. a first peripherally continuous bearing and coupling member surrounding said one portion of the cargo tank shell, laterally spaced outwardly with respect thereto, and having a substantially vertical orientation,

E one edge of the first peripherally continuous bearing and coupling member being continuously and rigidly connected to the protrusion nearer the vertical axis of the cargo tank,

3. a second bearing and coupling member surrounding the first bearing and coupling member, spaced laterally outwardly with respect thereto, and having a substantially vertical orientation,

a. the upper and lower edges of said second bearing and coupling member being continuous and one of said edges being rigidly and continuously connected to the peripherally continuous protrusion remote from the vertical axis of the cargo tank,

4. supporting structural means for mounting the cargo tank in a marine vessel for transportation thereby or for storage adapted to be fixed to the structure of the marine vessel, said supporting structural means rigidly and continuously interconnecting the other edges of said bearing and coupling members at a location vertically spaced from said peripheral structure means with said bearing and coupling members vertically extending from said peripheral structure means to said location free of interconnecting structure and vertically unstiffened, and

5. said peripheral structure means, said bearing and coupling members and said supporting structural means being constructed and arranged to interconnect the cargo tank shell to a marine vessel and to co-act so that in repose one of the bearing and coupling members is in compression and the other bearing and coupling member is in tension,

a. to check all movements of the tank relative to the marine vessel,

b. to prevent high stresses being induced in the tank shell or any bearing or supporting structure as a consequence of dimensional changes of the tank shell due to temperature differentials,

c. to reduce strongly bending moments in the tank shell, and

d. to prevent stress concentrations from occurring where the tank shell connects with support structure.

2. The combination as defined in claim 1 wherein said two peripherally continuous protrusions are laterally spaced from the lower portion of the cargo tank, the upper edge of each of said first and second peripherally continuous bearing and coupling members is continuously and rigidly connected to its respective protrusion, and said bearing and coupling members vertically depend downwardly from said peripheral structure means.

3. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said upper and lower continuous stubs projecting from the end of said web nearer said central vertical axis.

4. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said lower stub projecting downwardly from the end of said web nearer said central vertical axis and said upper stub projecting upwardly from the end of said web remote from said central vertical axis.

5. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, and said upper and lower continuous stubs of said continuous peripheral structure means projecting from the end thereof nearer said central vertical axis.

6. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said lower stub of said continuous peripheral structure means projecting from the end thereof nearer said central vertical axis and said upper stub projecting from the end thereof remote from said central vertical axis.

7. The combination as defined in claim 2. wherein said continuous peripheral structure means is defined by an open section, said bearing and coupling members are continuous throughout their height over their entire peripheries and define with said open section and said supporting structural means a conduit whereby a coolant fiuid may be circulated.

8. The combination as defined in claim 2 wherein said continuous peripheral structural means is comprised of three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, and said intermediate shells being continuous and defining in combination with said three sections a conduit whereby a coolant fiuid may be circulated.

9. The combination as defined in claim 1 wherein said tank shell has the shape of a body of revolution, the axis of revolution being vertical, and the spacings of the said two peripheral continuous protrusions and said first and second bearing and coupling members are radial relative to the vertical axis of revolution.

10. The combination as defined in claim 9 wherein said two peripherally continuous protrusions are radially spaced from the lower portion of the cargo tank, the upper edge of each of said first and second peripherally continuous bearing and coupling members is continuously and rigidly connected to its respective protrusion, and said bearing and coupling members vertically depend downwardly from said peripheral structure means.

11. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said upper and lower continuous stubs projecting from the end of said web nearer said vertical axis of revolution.

12. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said lower stub projecting downwardly from the end of said web nearer said vertical axis of revolution and said upper stub projecting upwardly from the end of said web remote from said vertical axis of revolution.

13. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different radial spacing relative to said vertical axis of revolution, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said upper and lower continuous stubs of said continuous peripheral structure means projecting from the end thereof nearer said vertical axis of revolution.

14. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different radial spacing relative to said vertical axis of revolution, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said lower stub of said continuous peripheral structure means projecting from the end thereof nearer said vertical axis of revolution and said upper stub projecting from the end thereof remote from said vertical axis of revolution.

15. The combination as defined in claim 1 wherein said first peripherally continuous bearing and coupling member is vertically continuous throughout its height over its entire periphery. 

1. The combination comprising:
 1. A cargo tank having a tank shell and a central vertical axis, said cargo tank adapted to contain liquified gas and including a. continuous peripheral structure means having upper and lower continuous stubs integrally connected with upper and lower portions, respectively, of the cargo tank shell thereby forming an annular portion of the tank shell in the vicinity of the horizontal mid-plane of the cargo tank, said continuous peripheral structure means extending in a lateral sense with respect to the vertical axis of the cargo tank and
 1. defining two peripherally continuous protrusions each laterally spaced from one of said portions of the cargo tank shell, said two continuous protrusions being spaced laterally relative to the vertical axis of the cargo tank and with respect to one another,
 2. a first peripherally continuous bearing and coupling member surrounding said one portion of the cargo tank shell, laterally spaced outwardly with respect thereto, and having a substantially vertical orientation, a. One edge of the first peripherally continuous bearing and coupling member being continuously and rigidly connected to the protrusion nearer the vertical axis of the cargo tank,
 3. a second bearing and coupling member surrounding the first bearing and coupling member, spaced laterally outwardly with respect thereto, and having a substantially vertical orientation, a. the upper and lower edges of said second bearing and coupling member being continuous and one of said edges being rigidly and continuously connected to the peripherally continuous protrusion remote from the vertical axis of the cargo tank,
 4. supporting structural means for mounting the cargo tank in a marine vessel for transportation thereby or for storage adapted to be fixed to the structure of the marine vessel, said supporting structural means rigidly and continuously interconnecting the other edges of said bearing and coupling members at a location vertically spaced from said peripheral structure means with said bearing and coupling members vertically extending from said peripheral structure means to said location free of interconnecting structure and vertically unstiffened, and
 5. said peripheral structure means, said bearing and coupling members and said supporting structural means being constructed and arranged to interconnect the cargo tank shell to a marine vessel and to co-act so that in repose one of the bearing and coupling members is in compression and the other bearing and coupling member is in tension, a. to check all movements of the tank relative to the marine vessel, b. to prevent high stresses being induced in the tank shell or any bearing or supporting structure as a consequence of dimensional changes of the tank shell due to temperature differentials, c. to reduce strongly bending moments in the tank shell, and d. to prevent stress concentrations from occurring where the tank shell connects with support structure.
 2. a first peripherally continuous bearing and coupling member surrounding said one portion of the cargo tank shell, laterally spaced outwardly with respect thereto, and having a substantially vertical orientation, a. One edge of the first peripherally continuous bearing and coupling member being continuously and rigidly connected to the protrusion nearer the vertical axis of the cargo tank,
 2. The combination as defined in claim 1 wherein said two peripherally continuous protrusions are laterally spaced from the lower portion of the cargo tank, the upper edge of each of said first and second peripherally continuous bearing and coupling members is continuously and rigidly connected to its respective protrusion, and said bearing and coupling members vertically depend downwardly from said peripheral structure means.
 3. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said upper and lower continuous stubs projecting from the end of said web nearer said central vertical axis.
 3. a second bearing and coupling member surrounding the first bearing and coupling member, spaced laterally outwardly with respect thereto, and having a substantially vertical orientation, a. the upper and lower edges of said second bearing and coupling member being continuous and one of said edges being rigidly and continuously connected to the peripherally continuous protrusion remote from the vertical axis of the cargo tank,
 4. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said lower stub projecting downwardly fRom the end of said web nearer said central vertical axis and said upper stub projecting upwardly from the end of said web remote from said central vertical axis.
 4. supporting structural means for mounting the cargo tank in a marine vessel for transportation thereby or for storage adapted to be fixed to the structure of the marine vessel, said supporting structural means rigidly and continuously interconnecting the other edges of said bearing and coupling members at a location vertically spaced from said peripheral structure means with said bearing and coupling members vertically extending from said peripheral structure means to said location free of interconnecting structure and vertically unstiffened, and
 5. said peripheral structure means, said bearing and coupling members and said supporting structural means being constructed and arranged to interconnect the cargo tank shell to a marine vessel and to co-act so that in repose one of the bearing and coupling members is in compression and the other bearing and coupling member is in tension, a. to check all movements of the tank relative to the marine vessel, b. to prevent high stresses being induced in the tank shell or any bearing or supporting structure as a consequence of dimensional changes of the tank shell due to temperature differentials, c. to reduce strongly bending moments in the tank shell, and d. to prevent stress concentrations from occurring where the tank shell connects with support structure.
 5. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, and said upper and lower continuous stubs of said continuous peripheral structure means projecting from the end thereof nearer said central vertical axis.
 6. The combination as defined in claim 2 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said lower stub of said continuous peripheral structure means projecting from the end thereof nearer said central vertical axis and said upper stub projecting from the end thereof remote from said central vertical axis.
 7. The combination as defined in claim 2 wherein said continuous peripheral structure means is defined by an open section, said bearing and coupling members are continuous throughout their height over their entire peripheries and define with said open section and said supporting structural means a conduit whereby a coolant fluid may be circulated.
 8. The combination as defined in claim 2 wherein said continuous peripheral structural means is comprised of three continuous sections having horizontal and parallel peripheries of different lateral spacing relative to said central vertical axis, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, and said intermediate shells being continuous and defining in combination with said three sections a conduit whereby a coolant fluid may be circulated.
 9. The combination as defined in claim 1 wherein said tank shell has the shape of a body of revolution, the axis of revolution being vertical, and the spacings of the said two peripheral continuous protrusions and said first and second bearing and coupling members are radial relative to the vertical axis of revolution.
 10. The combination as defined in claim 9 wherein said two peripherally continuous protrusions are radially spaced from the lower portion of the cargo tank, the upper edge of each of said first and second peripherally continuous bearing and coupling members is continuously and rigidly connected to its respective protrusion, and said bearing and coupling members vertically depend downwardly from said peripheral structure means.
 11. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said upper and lower continuous stubs projecting from the end of said web nearer said vertical axis of revolution.
 12. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises an open section characterized by a continuous substantially horizontally extending web from which said upper and lower continuous stubs and said two continuous protrusions project, said lower stub projecting downwardly from the end of said web nearer said vertical axis of revolution and said upper stub projecting upwardly from the end of said web remote from said vertical axis of revolution.
 13. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises three continuous sectioNs having horizontal and parallel peripheries of different radial spacing relative to said vertical axis of revolution, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said upper and lower continuous stubs of said continuous peripheral structure means projecting from the end thereof nearer said vertical axis of revolution.
 14. The combination as defined in claim 10 wherein said continuous peripheral structure means comprises three continuous sections having horizontal and parallel peripheries of different radial spacing relative to said vertical axis of revolution, which sectionally define the vertices of a triangle, said three sections being interlinked by means of intermediate shells defining the sides of the triangle, said lower stub of said continuous peripheral structure means projecting from the end thereof nearer said vertical axis of revolution and said upper stub projecting from the end thereof remote from said vertical axis of revolution.
 15. The combination as defined in claim 1 wherein said first peripherally continuous bearing and coupling member is vertically continuous throughout its height over its entire periphery. 